Photographic printing element



June 6,1'933. wg C, HUEBN'ER 1,912,482

PHOTOGRAPHIC PRINTING ELEMENT.

Filed June 6. 1928 Wi i 72 563 Patented June 6, 1933 UNITED STATESPATENT ori-lcs WILLIAM C. HUEBNER, OF CHICAGQILOLINOIS PHOTOGRAPHICPRINTING ELEMENT Application filed June 6, 1928.l Serial No. 283,201.

This invention relates to improvements'r in photographic printingelement, and more particularly to photographic printing plates havingcorrected values, for use in making press plates on photo-composingmachines.

In the commercial printing art, a great many of the printing or pressplates used are made by photographic process, as for instance, pressplates for offset printing presses in which most of the commercial colorprinting is now done. One of the most dificult steps, requiring thehighest degree of training and skill in the preparation of such plates,is that \of retouchingfl As well known, when a glass or film negativehas been made of the subject or image ultimately to be reproduced byprinting, almost invariably certain areas of the negative will require areduction of the values and other areas an increase of values in orderthat the proper values corresponding with'the original subject, may heobtained from the printing inks in the printed product, and it is theprovince of the retoucher to estimate or determine the amounts of suchincrease or reduction and to treat the negative accordingly by any ofthe known methods.

Heretofore, the retoucher has always been very seriously handicapped indetermining the extent of changes necessary in the values, primarilybecause there has been no available background or contrasting surfacebeneath the lm proper ofthe negative, since the negative has always,heretofore, been transparent, it having been the universal belief thatcompletely transparent negatives were necessary in the art.Consequently, as the retoucher has endeavored to, say, 'reduce the sizeof the 'actinically hardened very a minute dots or particles of thephotographic film coating (which dots or particles correspond to theultimate ink-conveying or printing units on the press plate) he has beenunable to obtain a direct basis of comparison of such dots or-particles,or corre.- sponding printing units, with a white surface on which theprinting is later to be done. Hence retouching has always involved muchuncerifainty, even by the most skilled worker, and has required thetaking of numerous proofs or trial impressions and the retouchin'g overand over of the negative, or corresponding positive, or both, before thefinal photographic printing plate has been considered satisfactory foruse in photo- 5a graphing directly on the press plate. Obviously, thediliiculties and disadvantages referred to involve excessive labor andtime, resulting in high cost.

The foregoing difliculties and disadvantages have been stated asapplying to the making of a single photographic printing plate as, forinstance, when only a single color impression is to be made. Whenmulti-color print-ing is considered and which involves the making of acolor separation negative for each ofthe color inks to be printed with,it will beseen that the diiiiculties in the retouching step aregreatly/multiplied. All of the colorseparation nega-tives orcorresponding 7U positives may be retouched until each alone appears tobe satisfactory but upon obtaining proofs of the several colorimpressions, it

is frequently discoveredrthat corresponding areas of two (or more) ofthe negatives will 7: require retouching,r.where t-he separate colorsare combined in the printing to produce a color intermediate the twoseparate colors.

An object of my invention, therefore, is to provide a new article ofmanufacture by 8U which photographic printing elements, negatives orpositives, such as used in the making of press plates, having correctedvalues, may be produced in less time, at less expense, with greater easeand greater certainty thanhere- 8 5 tofore. f

Another object of my invention is `to provide a special photographicprinting element,'negative or positive, characterized by the fact thatit will both transmity and diffuse light rays andalso afford a'comparison background immediately beneath the developed photographicfilm proper.

Other objects of the invention will more clearly appear from thedescription and claims hereinafter following.

In the drawing forming a part of this specification, Figure l is a planview of a photographic'glass plate negative, having my improvementsincorporated therein, this of illustration is greatly magnified in orderto clearly illustrate the invention.

In the preferred manner of carrying out my invention, I first take aglass plate of the character and quality commonly heretofore.substantially pure white and semi-opaque andused for photographicnegatives and having the usual transparent and light-transmittingcharacteristics, this main glass plate being indicated by the reference10. As will be understood, the same will be of any desired sizecorresponding to the size of the subject to be reproduced orphotographed, of suitable thickness, and smooth and polished, ascustomary in the art.

'lhe plate 10 is ,then preferably sprayed with a low point fusibleglass, to provide a very thin film or layer thereof over one entiresurface or side of the plate. This film or layer of low point fusibleglass, commercially obtainable in a very fine comminuted condit-ion,suspended in oil, is then fired, thusv evaporating the oil or othermedium of suspension and leaving a permanently affixed, Very thin, layeror film of the fused glass on the surface of the plate l0, which film orlayer is indicated by the reference 11, on that exposed portion of theplate in- Figure 1. The fused glass layer or film thus obtained ispreferably the layer or film will be of approximately .001 or .002 of aninch in thickness, this thickness being, of course, greatly exaggeratedin Figures 2 and 3. Another characteristic of the fused glass film orlayer is that it presents a grained or very minutely toothed surfaceeffect which, in turn, is of extreme importance in connection with myinvention for two principal reasons. One reason is that the grained orminutely toothed surface effect provides an excellent surface for theretention or anchoring thereto of the chemical solutions later appliedand which form the light-sensitive or photographic film proper. Thesecond is that the grains or minute tooth-like projections, whilepermitting the ready transmission of light through the fused glass layerand main plate 10, nevertheless effectively serve to cause a certainamount of diffusion of the light when impinging upon the said grainedsurface, the function of this being brought out hereinafter.

After the plate 10 has been prepared with its fused glass layer 11, acoating of lightsensitive film 12, preferably having an albumen base, isapplied, the negative then being ready for exposure.

In making the exposure, a previously taken negative of the subject orimage to be reproduced and which may be a color separation negative,taken through a half-tonescreen, if for color printing, is then placedin close or intimate contact with the film side of my improvedphotographie plate. A layer ol': velvet, felt, or equivalent material,capable of absorbing light rays and preventing reflection or refractionthereof, is placed on the opposite or non-film side of the photographieplate. The exposure is then made.

To the exposed photographic printing plate, is then applied, as byrolling, a layer of prin ting ink, preferably an ink having very littlevarnish and characterized by a short drying period and opaque.

After the layer of opaque ink has dried, the now exposed and inkedphotographie plate is then placed in a water bath and developed. Thoseportions of the sensitive film acted upon by the actinic rays will, asWell understood in the photographic art, be hardened, thus producingthroughout the photographic film proper, myriads of hardened dots orparticles such as indicated at 13, 14 and l5. in Figure 2, and whichdots or particles correspond to the ink-conveying dots or unitsultimately appearing on the printing or press plate, as will beunderstood by those skilled in the art.

The photographic plate, after being developed and in the bath, as aboveindicated, has all of the surplus ink removed and also those portions ofthe photographie film properwhich were not acted upon by the light, saidsurplus ink and soft portions of' the photographic film proper beingwashed away, thus leaving on the surface of the. photogra hic plate, amyriad of dots or units 15, from between which have been removed thesoft or non-actinically treated portions 16-16 of the film proper.

During the exposure of the photographic plate, a certain amount of thelight rays is 'diffused by the fused glass film ll. thus producing withrespect to each of the dots or particles 13, 14, 15, an adjacent area,as indicated at 17, which is semi-hardened by the actinic action and inthe removal and washing away of thesurplus ink and film coating` theseportions of semi-hardened film 17 will remain, as will be understood.

The next step in the treatment of the plate. is that of the retouehingafter the portions 16 of the film 12 have.bee n removed. The plate,lstill in the Water bath, -is then treated frictionally on those areaswhere a reduction in the values (that is, size) of the ink-conveyors orunits is desired. This frictional treatment may be done in 'any suitablemanner, as by the use of camel hair brushes, erasers or rolled paperstumps. Referring to Figure 3, the ink-conveying unit or particle 13 isshown as the same as when the plate was developed and washed. -The nextadjacent unit 114 is shown with its value or size reduced, as by removalof the portions 17 which were immediately adjacent the same at the endof the developing and Washing step. In this connection, due to thesurrounding portions 17 produced by the diffused light being onlysemi-hardened, they maybe readily removed bythe frictional action, thusfacilitating and speeding up the operation.

After the reduction of the values in those areas where desired, thephotographic plate is then taken out of the bath and dried, after whichthe ink dots or portions are coated with lamp black or other suitableopaque mixture. In those portions or areas Where the values require anincrease, said areas or portions are filled in by a lithographievcrayon, opaque ink, or other suitable substance, capable of blocking thepassage of light, as well understood in the art', thus increasing thesizes, as indicated at 115 in Figure 3.-

rIhe photographic plate is now completed and corrected, as to values,and ready for exposure, either against another negative or, if desired,directly against a sensitized press plate and on either of which will be-reproduced photographically the ink-conveying units, dots or particleshaving the desired and corrected values to produce the final print.

In the event the corrected value photographic plate is to have the imagethereon transferred to another negative, the two film surfaces arebrought into intimate conta-ct and a lay- .er of velvet, felt orequivalent light-absorbing material placed on the back side of thenegative to be exposed, the lightbeing passed through the preparedphotographic plate when making the exposure. As will be understood, thenegative to which-the image is transferred in the illustration referredto, may be of glass, film, paper or other suitable material.

By preparing the photographic plates'with the white light-transmittingand diffusing film of fused glass 11, the semi-hardening of thesensitive film proper, as above described,

is obtained and in addition the retoucher has available in correctingthe values, a white surface immediately adjacent the ink-conveying unitsor particles so as to obtain a direct contrast or background for theunits or-pa-rticles and by which he is enabled to correctly judge theamount or degree to which the ink-conveying units shall be increased ordecreased With reference to the white paper on which the printing isultimately to be done. In this manner, greater accuracy as to thedesirable values is obtained more quickly than in any of the heretoforeknown methods of retouching or value correcting methods and hence, thecost of producing the printing plate is correspondingly reduced.

In actual practice, when the fused layer or film of glass hasbeen-applied to the main glass plate,thesamewillbethoroughlywashed filmof such a thickness as to just cover the grains or toothlike projectionsof the fused layer, this initial sensitive film then being.

hardened throughout by exposing the same and developing, after which asecond film or layer or sensitized material will be applied on the firstlayer or film and the exposures then made, as hereinbefore described.

Another expedient sometimes employed where the printing units or dots onthe ori ginal negative are too large in certain areas and it is desiredto reduce the values there/of in making my improved plate, is to stainthe desired areas of the original negative with a red aniline dye, thestrength of the latter being graduated in proportion to the degree ofreduction required. As will be understood by those skilled in the art,where the original negative is a color separation negativ-e withhalf-tone dots, the application of the dye to the desired areas willreduce the amount of light that may be transmitted therethrough when theexposure is made against my im-l standpoint of expansion or contraction,and

also because it retains its White semi-opacity even when wet. I amaware, however, that a film or layer having semi-opaque,light-transmitting the light-diffusing characteristics may otherwise beobtained, as for instance, by the use of a white lacquer suitablyreduced by proper solvents that will dry out, thus leaving the -desiredfilm.

I claim':

1. As an article of manufacture, a photographic printing plate forretouching, said plate having the main portion thereof composed of glassof customary transparent and smooth surface characteristics and providedon one face thereof with an applied, extremely thin, semi-opaque filmwhich remains substantially pure white under dry and wet conditions andthrough which light is adapted to be uniformly transmitted and slightlydiffused; and exposed, light-hardened and developed particles of apreviously applied light-sensitive film on said semi-opaque film, thenon-hardened areas of said previously applied light sensitive film beingremoved to thereby leave the corresponding areas of the semi-opaque filmdirectly visible, said directly llO visible areas of the semi-opaquefilm prescntv for said light-hardened particles to thereby provide acomparative surface when the plate is being retouched While either Wetor dry.

2. As an article of manufacture, a photographic printing plate forretouching, said plate having the main portion thereof composed of glassof customary transparent characteristics and provided on one facethereof with an applied, extremely thin, substantially pure white,semi-opaque film of fused glass and which film is adapted for uniformtransmission of light therethrough and slight diffusion; and a layer oflight-sensitive film applied on said semi-opaque fused glass film, saidsemi-opaque fused ilm presenting a substantially pure White background,While either dry or Wet, for the lightsensitive film to thereby providea comparative surface while the plate is being retouched.

3. A photographic printing element for photographically printing afterthe values thereon have' been -corrected by retouching, said elementcomprising: a transparent foundation layer; a thin, substantially purewhite, uniform, light-transmitting, light-diffusing, semi-opaque, layerextending over and adhered to one surface of the foundation layer, saidsemi-opaque layer being of material unatl'ectcd by light and retainingits whiteness when both wet and dry; and exposed, lighthardened anddeveloped particles of a previously applied light-sensitive ilm on saidsemi-opaque film, the non-hardened areas of said previously appliedlight sensitive film being ren'ioved to thereby leave the correspondingarcas of the semi-opaque film directly visible, said directly visiblearcas of the white semi-opaque layer, While dry or wet` presenting asubstantially white comparative background for retouching saidlight-hardened particles.

. In witness that I claim the foregoing I have hereunto subscribed myname this 23rd day of May, 1928.

WILLIAM C. HUE BNER.

